The Ethereal doesn’t border the Outer Planes, and thus spells that allow you to access the Ethereal fail. However some creatures or objects have Ethereal parts to them. What happens to them?
For examples of how this situation can arise:
in one adventure set in the Outlands, there is a living trap of scorpions disguised as gold coins. The stingers are described as “Ethereal” even though it takes place on the Outlands. (Or was this detail a mistake?)
an Ethereal weapon or creature is forced through a portal